1. Field of the Invention
This invention relates generally to a satellite communication system and, more particularly, to a method for discriminating and routing data packets based on quality of service (QoS) requirements of the providing application.
2. Discussion of the Related Art
Modern communication systems are primarily based on packet switching networks which are able to support voice, video and other data types all within the context of the same network infrastructure. A relatively small amount of the communication traffic, such as voice traffic, puts a very high demand on the system to handle stringent quality of service (QoS) requirements (e.g., latency). On the other hand, a larger percentage of the communication traffic does not need to meet QoS requirements. In these instances, the non-QoS data packets merely require retransmission and intermediate data buffering when errors occur in the communication link.
Therefore, it is desirable to provide a communication system that utilizes two or more network services that are each optimized to handle a different type of communication traffic. For instance, voice data packets may be directed to a narrow band network service; whereas non-QoS data packets may be diverted to a broadband network offering best effort delivery service. Discriminating and routing data packets based on QoS requirements is of particular importance in satellite-based communication systems where orbital designs must accommodate the need for short round trip times required for voice data.
Low earth orbiting (LEO) satellite systems generally offer advantages over geosynchronous orbiting (GEO) satellite systems for the delivery of QoS data packets. The advantages primarily stem from an orbit selection that facilitates the use of low-power transmitting devices as well as reduces the long propagation delays inherent in GEO satellites systems. However, the number of LEO satellites needed to cover a relatively large service area is considerably more than those required to cover a comparable service area in a GEO satellite system. Therefore, LEO satellite systems are usually optimized for only voice data and other QoS data packets.
On the other hand, GEO satellite systems generally offer advantages for delivery of non-QoS data packets needing best effort delivery service. Its orbit selection allows a single GEO satellite to serve a relatively large service area, thereby reducing the cost of deployment. In order to support a best effort delivery service, GEO satellites are configured with minimal on board circuitry which is needed for retransmission and data buffering of data packets when an error occurs in the communication link. Thus, GEO satellite systems are best suited to handle streaming video, file transfer, multicasting, and other typically broadband IP-based data packets.
Accordingly, there is a need for the ability to discriminate among the different types of data packets (i.e., QoS and non-QoS data packets) that are being transmitted in a satellite-based communication system. A mobile network routing device is used to route the data packets to an appropriate communication infrastructure. The present invention routes the data packets based on the QoS requirements associated with the application providing the data packets. In addition, the invention relies on a unique physical layer that implements synchronized time division duplex, spread-spectrum connections that are channelized by CDMA techniques.
In accordance with the present invention, a method is provided for discriminating and routing data packets in a satellite-based communication system, comprising the steps of: (a) receiving an input data stream from an application residing on a transmitting device; (b) selecting either a first spread spectrum code or a second spread spectrum code based on the quality of service (QOS) requirements associated with the first application; (c) applying the selected spread spectrum code to the input data stream, thereby generating. a spread spectrum data stream; (d) transmitting the spread spectrum data stream from the transmitting device to a network routing device; (e) correlating the spread spectrum data stream with the corresponding selected spread spectrum code to recover the original input data stream; and (f) routing the input data stream to either a low earth orbiting satellite when the first spread spectrum code is used to recover the input data signal or to a geosynchronous orbiting satellite when the second spread spectrum code is used to recover the input data signal.